Atrial fibrillation is a significant and prevalent medical problem. Several nonpharmalogical percutaneous transcatheter therapeutic approaches have been specifically designed in attempts to solve this problem. One such approach is electrical isolation of the pulmonary veins, which is especially suitable for cases where autonomous foci in the pulmonary veins exist. These foci may trigger paroxysmal atrial fibrillation or may sustain the fibrillation.
The following references, which are incorporated herein by reference, may be useful:
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Natale A; Pisano E, Shewchik J, Bash D, Fanelli R, M D; Potenza D; Santarelli P; Schweikert R; White R; Saliba W; Kanagaratnam L; Tchou P; Lesh M. First Human Experience With Pulmonary Vein Isolation Using a Through-the-Balloon Circumferential Ultrasound Ablation System for Recurrent Atrial Fibrillation Circulation 2000;102:1879-1882.
U.S. Pat. No. 6,457,365 to Stephens, et al., whose disclosure is incorporated herein by reference, describes an ultrasound transducer array including at least one transducer element having first and second portions separated by an acoustical discontinuity. The first portion has the desired length to form a half-wave k31 resonance, while the second portion has a resonant length for an undesired very low frequency out-of-band k31 resonance. The thickness of the transducer element is designed for k33 half-resonance. Given the design, the transducer element can operate and provide for both forward-looking and side looking elevation apertures. A method is also disclosed for using the disclosed ultrasound transducer in ultrasound imaging.
U.S. Pat. No. 6,524,271 to Brisken, et al., whose disclosure is incorporated herein by reference, describes a method for treating a target region in a body lumen, including: directing a uniform dose of ultrasonic energy from an interior of the lumen radially outward over a treatment length of the lumen, wherein the dosage of ultrasonic energy received at any one point along the length varies by no more than plus or minus 6 decibels from that received at any other point along the length.
U.S. Pat. No. 6,416,511 to Lesh, et al., whose disclosure is incorporated herein by reference, describes a circumferential ablation device assembly, which is adapted to form a circumferential conduction block in a pulmonary vein.
U.S. Pat. No. 6,251,109 to Hassett, et al., whose disclosure is incorporated herein by reference, describes a process for treatment of atrial arrhythmia by ablation of pulmonary veins via an ablation catheter located within one of a pair of balloons secured to the catheter.
U.S. Pat. No. 6,117,101 to Diederich and Lesh, et al., whose disclosure is incorporated herein by reference, describes a circumferential ablation device which is adapted to form a circumferential conduction block in a pulmonary vein by producing a radial ultrasound signal inside a balloon such that the ultrasound signal couples to the balloon's outer skin and ablates tissue in contact with the balloon's outer skin.
U.S. Pat. No. 6,652,515 to Maguire et al., whose disclosure is incorporated herein by reference, describes a circumferential ablation device, which is adapted to form a circumferential conduction block in a pulmonary vein by applying thermal, light or ultrasound energy to ablate tissue. Directional control of ultrasound ablation is attempted through rotation of a planar ultrasound source or by applying various coatings to a balloon in which the ultrasound source is affixed.
U.S. Pat. No. 5,938,660 to Swartz, et al., whose disclosure is incorporated herein by reference, describes a process and devices for treating atrial arrhythmia by circumferential ablation of vessels including the pulmonary veins.
U.S. Pat. No. 5,295,484 to Marcus, et al., whose disclosure is incorporated herein by reference, describes a device for delivering ultrasonic energy to myocardial tissue so as to destroy myocardial tissue implicated in an arrhythmia.